Mr. Fantastic or also known as Reed Richards, has a high Genius-level intellect and has extreme superhuman elasticity , malleability and endurance. He has resistance on most physical attacks and electricity.Also immune to psyhic powers as well.Source here
image sourceHe is the son of a scientific genius which he inherited te same level of intellect and interest. He is really good at mathematics , physics and mechanics.He has a rivalry with Victor Von Doom in terms of intelliect which they compete on experiments and academic. In a fateful mission he and the rest of the crew including Ben Grimm, Susan Storm and Johnny Storm got their super powers. He was once a member of Avenger them but decided to clear his own team the Fantastic Four.Source here